Compaction System and Method for Determining Roller Decoupling

ABSTRACT

A compaction system and a method for determining decoupling of a roller from a work material are disclosed. The compaction system includes a roller configured to compact a work material through rolling engagement with the work material. The compaction system also includes a propulsion device configured to propel the roller along the work material, a power source operatively coupled to the propulsion device, a sensor configured to generate a signal that is indicative of a power potential from the power source, and a controller operatively coupled to the sensor. The controller is configured to receive the signal from the sensor, determine a first variance for a first time duration of the signal, determine a second variance for a second time duration of the signal, and determine the roller is decoupled from the work material based on at least one of the first variance and the second variance.

TECHNICAL FIELD

This patent disclosure relates generally to a compaction system and method for determining roller decoupling, and more particularly, to a compaction system and method for determining roller decoupling by a sensor coupled to the roller.

BACKGROUND

Compacting machines or compactors are commonly used to compact work materials, such as soil, gravel, asphalt, and the like, to a desired stiffness or density during the construction of buildings, highways, parking lots, and other structures. In addition, compactors are often used to compact recently moved and/or relatively soft materials at mining sites and landfills. The compaction process often requires several passes over the work material to reach the desired stiffness or density.

Often, it is necessary for an operator of the compactor to determine a state of compaction of the work materials. Otherwise, the operator may waste time and resources in performing too many or too few passes across the work material. The amount of compaction of these materials must be monitored by some means to determine when the work material has been compressed to a desired stiffness or density. In the past, various methods for determining an amount of compaction have been employed. Some of these methods involve the usage of an accelerometer coupled to the compaction system. Other methods have been developed to provide more accurate readings of the compaction state, such as relying on the rolling resistance of the compaction system.

U.S. Pat. No. 6,188,942 (the '942 patent) entitled “Method and Apparatus for Determining the Performance of a Compaction Machine Based on Energy Transfer,” discloses a method for determining a state of compaction of a work material based on rolling resistance. Specifically, as disclosed by the '942 patent, the compaction performance may be determined as a function of compactive energy or as a function of the propelling power of the compactor. The compaction system disclosed in the '942 patent may give more consistent measurements of the stiffness or density of the work material compared to traditional methods that use accelerometers. However, such a compaction system may not include an accelerometer to rely upon to determine decoupling of the roller from the work material.

Accordingly, there is a need for improved compaction systems and methods to address the aforementioned problems and/or other problems known in the art.

The foregoing background discussion is intended solely to aid the reader. It is not intended to limit the innovations described herein, nor to limit or expand the prior art discussed. Thus, the foregoing discussion should not be taken to indicate that any particular element of a prior system is unsuitable for use with the innovations described herein, nor is it intended to indicate that any element is essential in implementing the innovations described herein. The implementations and application of the innovations described herein are defined by the appended claims.

SUMMARY

According to an aspect of the disclosure, a compaction system includes a roller configured to compact a work material through rolling engagement with the work material, a propulsion device configured to propel the roller along the work material, a power source operatively coupled to the propulsion device, a sensor configured to generate a signal that is indicative of a power potential from the power source, and a controller operatively coupled to the sensor. The controller is configured to receive the signal from the sensor, determine a first variance for a first time duration of the signal, determine a second variance for a second time duration of the signal, and determine the roller is decoupled from the work material based on at least one of the first variance and the second variance.

According to another aspect of the disclosure, a method for determining decoupling of a roller from a work material includes compacting the work material with a roller driven by a propulsion device, receiving a signal from a sensor, the signal indicative of a power potential of a power source operatively coupled to the propulsion device, determining a first variance for a first time duration of the signal, determining a second variance for a second time duration of the signal, and determining a roller is decoupled from the work material based on at least one of the first variance and the second variance.

According to yet another aspect of the disclosure, an article of manufacture includes non-transient machine-readable instructions encoded thereon for causing a controller to forward instructions to compact a work material with a roller driven by a propulsion device, receive a signal from a sensor, the signal indicative of a power potential of a power source operatively coupled to the propulsion device, determine a first variance for a first time duration of the signal, determine a second variance for a second time duration of the signal, and determine a roller is decoupled from the work material based on at least one of the first variance and the second variance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a machine according to an aspect of the disclosure.

FIG. 2 is a schematic diagram of a compaction system according to an aspect of the disclosure.

FIG. 3 is a flowchart for a process of the compaction system according to an aspect of the disclosure.

FIG. 4 is a graph of a signal received from a sensor according to an aspect of the disclosure.

DETAILED DESCRIPTION

Aspects of the disclosure will now be described in detail with reference to the drawings, wherein like reference numbers refer to like elements throughout, unless specified otherwise.

FIG. 1 illustrates a machine 100 that may be used for compacting a work material 102, such as soil, gravel, asphalt, or other materials. The machine 100 may be a self-propelled single drum compactor having a single cylindrical drum or roller 104 for compacting the work material 102. The machine 100 includes a frame 106 and a prime mover or power source 108, such as an engine. The power source 108 may be coupled to a propulsion device or drivetrain system 110 (shown in FIG. 2) that propels the machine 100 across a work surface 112. The systems and methods of this disclosure may be used with any machine propulsion and drivetrain mechanisms applicable in the art including hydrostatic, electric, or mechanical drives. The propulsion device or drivetrain system 110 may include any components, such as a transmission, propeller shaft, axle, and the like, to operate the roller 104 and propel the machine 100 across the work surface 112 on one or more wheels 114. In other aspects, other types of work material 102 engaging members may be used such as replacing the wheels 114 with another roller 104.

As mentioned previously, the power source 108 may be an engine. The engine may be an internal combustion engine including a reciprocating piston engine, such as a compression ignition engine or a spark ignition engine, a turbomachine such as a gas turbine, combinations thereof, or any other internal combustion engine known in the art. In other aspects, the power source 108 may be an electric motor. The power source 108 may be operatively coupled to a controller 116 (shown in FIG. 2).

The roller 104 includes a vibration system 118 to impart a compacting force onto the work material 102. More specifically, in addition to the weight of the roller 104 and the machine 100 being applied to the work material 102, the vibration system 118 may operate to apply additional forces to the work material 102. As described herein, the vibration system 118 may include any type of system that imparts vibrations, oscillations, or other repeating forces through the roller 104 onto the work material 102.

The vibration system 118 may be operatively coupled to the power source 108 via a vibration drive system 120 (shown in FIG. 2). The vibration drive system 120 may be a hydraulic drive system, an electric drive system, a mechanical drive system, a hybrid drive system, or another drive system known in the art. The power source 108 may be the same component used to power the drivetrain system 110. In other aspects, a separate power source (not shown), such as an electric motor, may be configured to provide power to the vibration system 118. The vibration drive system 120 powered by the power source 108 may rotate one or more eccentrically mounted masses 122 within the roller 104 to create a vibrating or oscillatory force within the roller 104 that is imparted to the work material 102. In other aspects, the masses 122 may be moved linearly rather than eccentrically as part of a rotational system.

The machine 100 also includes at least one sensor 124 that may be operatively coupled to the drivetrain system 110 and/or vibration drive system 120 in order to measure a drive potential of the drivetrain system 110 and/or vibration drive system 120. In one aspect, the vibration drive system 120 may be a hydraulic drive system, and the sensors 124 may be configured to determine a hydraulic pressure signal of the vibration drive system 120. In another aspect, the vibration drive system 120 may be an electric drive system, and the sensors 124 may be configured to determine an electric potential signal of the vibration drive system 120. The sensors 124 may be operatively coupled to the drivetrain system 110 and/or vibration drive system 120 at various locations and configured to determine a drive potential those locations. For example, the sensor 124 may be coupled to an axle drive of the drivetrain system 110, the roller 104, a conduit 156 in the vibration drive system 120, and/or another suitable location. Other locations along the vibration drive system 120 and/or drivetrain system 110 are also contemplated.

The sensors 124 may forward a drive potential signal to the controller 116, which may use the signal to determine whether the roller 104 has decoupled from the work material 102. Compactor systems that use an accelerometer to control the vibration system typically will also use the accelerometer to detect roller decoupling. However, for compactors that may not rely on accelerometers for vibration control, the sensors 124 provide a more advantageous method for detection of roller decoupling. The sensors 124, which may be hydraulic pressure sensors or voltage sensors, may be simpler components and have a lower component cost compared to an accelerometer. Further, the sensors 124 may be more wear resistant compared to an accelerometer and less prone to failure.

The machine 100 may include an operator station 126 from which an operator may control the machine 100. The operator station 126 may include an operator interface 128 coupled to the controller 116 (shown in FIG. 2), through which the operator may issue commands to control power source 108, the drivetrain system 110, the vibration system 118, and/or other components of the machine 100. The operator interface 128 may include a plurality of input devices 132 including a throttle input, a transmission input, a speed input, a vibration frequency input, a vibration amplitude input, and the like. One or more of the input devices 132 may take the form of a joystick, a peal, a push-button, a knob, a switch, or another device. The operator may manipulate each input device 132 to affect corresponding operations of the machine 100. The operator interface 128 may include a display on which various types of information useful or necessary for the operation of the machine may be displayed.

The throttle input may be configured to generate one or more throttle input signals that are indicative of a desired percentage of the maximum speed of the machine 100 in a particular direction. In some aspects, the throttle input may be a joystick that is tiltable from a neutral position to one or more displacement positions to generate the one or more throttle input signals. For example, the throttle input may be tiltable from a neutral position to a maximum displacement position in a first direction (e.g., forward) to generate a corresponding first throttle signal. Likewise, the throttle input may be tiltable from the neutral position to a maximum displacement position in a second direction (e.g., rearward) to generate a corresponding second throttle signal. Values of the first throttle signal and the second throttle signal may depend on the displacement of the throttle input from the neutral position.

The transmission input may be used by an operator of the machine 100 to select one or any number of available transmission control settings of the drivetrain system 110, such as virtual gears or portions of a continuous range of available transmission speed-to-torque ratios. For example, an operator of the machine 100 may use the transmission input to select a first transmission gear, in which, the drivetrain system 110 may operate within a highest torque output range and a corresponding lowest ground speed range. Likewise, an operator of the machine 100 may select a second transmission gear, in which the drivetrain system 110 may operate with a lower torque output range and a corresponding higher ground speed range.

The speed input may be an input device 132 that allows an operator of the machine 100 to select one or any number of maximum allowable speeds or available machine 100 ground speed limits. The maximum allowable speeds or available machine 100 ground speed limits may correspond to the maximum displacement position of the throttle input as described above.

The vibration frequency input and vibration amplitude input may be used to control the operation of the roller 104 and vibration system 118. The vibration frequency input may be an input device 132 to configure the frequency of vibrations imparted on the work material 102 by the roller 104. More specifically, the vibration frequency input may be used to set the rate at which the masses 122 in the roller 104 move and thus the frequency at which the roller 104 impacts the work surface 112. The vibration amplitude input may be an input device 132 to configure the amplitude of vibrations imparted on the work material 102 by the roller 104. More specifically, the vibration amplitude input may be used to set the stroke of the masses 122 and thus establish the force of impact between the roller 104 and the work material 102.

The vibration system 118 may permit an infinite number of adjustments to both the vibration frequency and vibration amplitude or may have a predetermined number of pre-set values for either or both of the vibration frequency and the vibration amplitude. In one example, the vibration frequency may be set to low, medium, or high depending on the characteristics of the work material 102 upon which machine 100 is operating. In addition, the vibration amplitude may be set to low, medium, or high depending on the characteristics of the work material 102. In other instances, the vibration frequency and/or amplitude may be set to specific values based upon the characteristics of the work material 102.

FIG. 2 is a schematic diagram of a compaction system 101 of the machine 100, according to an aspect of the disclosure. Although FIG. 2 illustrates a hydraulic drive system, other systems, such as an electric drive system, a mechanical drive system, a hybrid drive system, etc., are contemplated. FIG. 2 illustrates the power source 108 operatively connected to a first hydraulic pump 134 and a second hydraulic pump 136. The first hydraulic pump 134 and the second hydraulic 136 may each be operatively coupled to power a first motor 138 and a second motor 140, respectively, via a first hydraulic line 142 and a second hydraulic line 144. The first motor 138 may be driven by hydraulic fluid from the first hydraulic pump 134 to power the drivetrain system 110 and rotate the wheels 114. The second motor 140 may be driven by hydraulic fluid from the second hydraulic pump 136 and rotate the roller 104. Additional pumps and motors may be utilized to provide power to additional components of the machine 100. Alternatively, the pumps 134, 136 and motors 138, 140 may also be consolidated to reduce the number of components of the machine 100.

The first hydraulic pump 134 and the second hydraulic pump 136 may each be a variable displacement pump with the displacement controlled by the controller 116. In one aspect, signals from the controller 116 may be used to control or adjust the displacement of the first hydraulic pump 134 and/or second hydraulic pump 136. The first hydraulic pump 134 and the second hydraulic pump 136 may each direct pressurized hydraulic fluid to and from their respective motors 138, 140 in two different directions to operate the motors 138, 140 in forward and reverse directions. The first hydraulic pump 134 and the second hydraulic pump 136 may each include a stroke-adjusting mechanism, such as a swashplate, the position of which can be hydro-mechanically or electro-mechanically adjusted to vary the output (e.g., a discharge pressure or rate) of the pumps 134, 136. The displacement of each of the first hydraulic pump 134 and the second hydraulic pump 136 may be adjusted from a zero displacement position, at which substantially no fluid is discharged from the pumps 134, 136, to a maximum displacement position, at which fluid is discharged from the pumps 134, 136 at a maximum rate. The displacement of each of the first hydraulic pump 134 and the second hydraulic pump 136 may be adjusted so the flow is either into its first hydraulic line 142 or its second hydraulic line 144 so that each pump 134, 136 may drive its respective motor 138, 140 in either forward and reverse directions, depending on the direction of fluid flow.

Each of first motor 138 and second motor 140 may be driven to rotate by a fluid pressure differential generated by its respective pump 134, 136 and supplied through first hydraulic line 142 and second hydraulic line 144. More specifically, each motor 138, 140 may include first and second chambers (not shown) located on opposite sides of a pumping mechanism such as an impeller, plunger, or series of pistons (not shown). When the first chamber is filled with pressurized fluid from the pump via first hydraulic line 142 and the second chamber is drained of fluid returning to the pump via second hydraulic line 144, the pumping mechanism is urged to move or rotate in a first direction (e.g., in a forward traveling direction). Conversely, when the first chamber is drained of fluid and the second chamber is filled with pressurized fluid, the pumping mechanism is urged to move or rotate in an opposite direction (e.g., in a rearward traveling direction). The flow rate of fluid into and out of the first and second chambers may determine an output velocity of the motor, while a pressure differential across the pumping mechanism may determine an output torque.

Each of first motor 138 and second motor 140 may be a variable displacement motor with the displacement controlled by controller 116. In that aspect, each of the motors 138, 140 has an infinite number of configurations or displacements. In another aspect, each of first motor 138 and second motor 140 may be a fixed and/or a multi-speed motor. In that aspect, each motor 138, 140 has a finite number of configurations or displacements (e.g., two) between which the motors 138, 140 may be shifted. The motors 138, 140 may thus operate as a fixed displacement motor with a plurality of distinct displacements.

The vibration drive system 120 may include a vibration system pump 146 and a vibration system motor 148, similar to the pumps 134, 136 and the motors 138, 140. Both the vibration system pump 146 and the vibration system motor 148 may be operatively coupled to the controller 116, which can control their operation in response to the vibration frequency input and vibration amplitude input described above. The vibration system pump 146 may be operatively coupled to the power source 108. As mentioned previously, the power source 108 may the same component or a different component as the component used to power the drivetrain system 110. For example, the power source 108 may include a combustion engine configured to propel the roller 104 and wheels 114 and also include an electric motor dedicated to power the vibration drive system 120 and rotate the masses 122.

The power source 108 may be configured to drive the vibration system pump 146, which is operatively connected to power the vibration system motor 148 via a first vibration system hydraulic line 150 and a second vibration system hydraulic line 152. The vibration system motor 148 may be configured to drive one or more shafts 154 in order to rotate the masses 122. The rotation of the masses 122 creates a vibrating and/or oscillatory force within the roller 104 that is imparted to the work material 102.

The compaction system 101 also includes at least one of the sensors 124. As mentioned previously, the sensors 124 may be configured to determine a potential of either the drivetrain system 110 and/or vibration drive system 120. In the hydraulic system illustrated in FIG. 2, the sensors 124 are configured to determine a hydraulic pressure signal. The sensors 124 are further configured to forward the potential signal to the controller 116, which may use the potential signals to control various components of the machine 100. In the aspect illustrated in FIG. 2, a sensor 124 may be coupled to the vibration drive system 120 at the conduit 156. Another sensor 124 may be coupled to the conduit 158, which connects the first motor 138 to the drivetrain system 110 and the wheels 114. It is understood that the location of the sensors 124 are shown for exemplary purposes only. Additional sensors 124 located at other locations are contemplated by the present disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to apparatus and methods for determining decoupling of the roller 104 from the work material 102 during operation of the machine 100. Referring to FIG. 1, the machine 100 may be configured to be propelled along a work surface 112 by the roller 104 and wheels 114. The machine 100 may be configured to engage and compact the work material 102 using the roller 104 and vibration system 118. During operation of the machine 100, the roller 104 may decouple from the work material 102 (e.g. loss of contact or irregular contact between the roller 104 and the work material 102) and not properly perform its compaction operation. Accordingly, it may be desirable to determine decoupling of the roller 104. Specifically, the power potential at various points in the drivetrain system 110 and/or vibration system 118 may become unstable when the roller 104 decouples from the work material 102. The sensors 124 may be used to monitor the power potential of the drivetrain system 110 and/or vibration system 118 and generate a signal reading to the controller 116. The controller 116 can receive these signals and subsequently determine whether the roller 104 has decoupled from the work material 102.

FIG. 3 is a flowchart of a process 200 for a compaction system 101, according to an aspect of the disclosure, and described in further detail below in reference to FIGS. 1-3. Although the process 200 is described with reference to FIG. 2, which illustrates a hydraulic compaction system, the process 200 may be performed by other compaction systems. The process 200 may be executed by the controller 116. The process 200 starts at step 202. In step 202, the compaction system 101 may compact a work material (e.g., work material 102) with the roller 104 of the machine 100. The controller 116 may forward instructions to control the compaction by the roller 104, such as instructions to set the frequency and amplitude of the compaction. The controller 116 may forward the instructions based on an input by an operator of the machine 100, such as the vibration frequency input and/or vibration amplitude input described above.

In step 204, the controller 116 may receive a signal from the sensor 124. The signal may indicate a power potential of the power source 108 coupled to the roller 104, drivetrain system 110, or vibration system 118. As mentioned before, the machine 100 may be powered through hydraulic, electric, or mechanical drives. The signal may indicate a power potential of the specific drive system. In one aspect, the machine 100 may operate using a hydraulic drive system, and the signal may be indicative of a hydraulic pressure at the sensor 124. In another aspect, the machine 100 may operate using an electric drive system, and the signal may be indicative of an electric potential at the sensor 124. In some aspects, the sensor 124 may continuously transmit the signal to the controller 116. In other aspects, the sensor 124 may periodically transmit a signal to the controller 116, such as every 100 milliseconds.

In step 206, the controller 116 may determine a first variance for a first time duration of the signal. The first variance may be a measure of the stability of the signal. In some aspects, the first variance may be a measure of the spread of the signal value during the first time duration, such as a statistical variance or standard deviation of the signal value. For example, the signal may have an average value of 200 kilopascal (kPa) with a standard deviation of 10 kPa during the first time duration. In this example, the first variance may be the standard deviation and have a value of 10 kPa.

In some aspects, the signal generated by the sensor 124 may exhibit sinusoidal-like behavior. One of ordinary skill in the art would be able to determine amplitude and frequency values for the signal. In another aspect, the first variance may be a measure of a peak to peak amplitude variance of the signal during the first time duration. In this example, the first variance may be a measure of the spread of the peak-to-peak average, such as a statistical variance of a standard deviation of the average peak-to-peak amplitude. In yet another aspect, the first variance may be a measure of the average frequency of the signal during the first time duration. Further, the first variance may be a measure of the spread of the average frequency of the signal during the first time duration, such as a statistical variance or a standard deviation of the average frequency. In further aspects, the first variance may be one or more of the foregoing measures. The descriptions of the first variance described herein are not intended to be limiting. The first variance may also be other measures of the signal's stability as understood by those of ordinary skill in the art.

In step 208, the controller 116 may determine a second variance for a second time duration of the signal. The second variance may be determined in the same manner as the first variance. For example, if the first variance is a standard deviation of the signal's frequency during the first time duration, the second variance would be a standard deviation of the signal's frequency during the second time duration.

In step 210, the controller 116 may determine the roller 104 is decoupled from the work material 102 based on at least one of the first variance and the second variance. When the roller 104 decouples from the work material 102, the signal received from the sensor 124 may change and become unstable. The first variance and/or second variance are measures of the stability of the signal and may be used to determine decoupling of the roller 104 from the work material 102. FIG. 4 illustrates an exemplary signal generated by the sensor 124 of a machine 100 according to an aspect of the present disclosure. In this example, the roller 104 may decouple from the work material 102 at the beginning of the second time duration t2. The controller 116 may determine a first variance for the first time duration t1 and determine a second variance for the time duration t2 to detect decoupling of the roller 104.

In one aspect, the controller 116 may compare the first variance and second variance and may determine the roller 104 has decoupled from the work material 102 when a difference between the first variance and the second variance exceeds a threshold. As mentioned previously, the first variance is a measure of stability of the signal during the first time duration. The first time duration may be a time duration where the roller 104 exhibits normal operating behavior and remains properly coupled to the work material 102. When the roller 104 decouples from the work material 102, the signal changes and the second variance at the second time duration may be different from the first variance. Although some change between the first variance and the second variance may be present even during normal operation, a difference between the first variance and the second variance that exceeds a predetermined threshold may indicate that the roller 104 has decoupled from the work material 102. Similarly, the controller 116 may determine the roller 104 has decoupled from the work material 102 when a ratio between the first variance and the second variance exceeds a first threshold.

In another aspect, the controller 116 may determine the roller 104 has decoupled from the work material 102 when a magnitude of the second variance exceeds a threshold. The controller 116 may have predetermined threshold value that corresponds to stable ranges of the compaction system 101. Values above the predetermined threshold value may indicate the roller 104 has decoupled from the work material 102. As mentioned previously, the second variance may be a peak-to-peak amplitude, a peak-to-peak amplitude variance, an average frequency, an average frequency variance, and the like. The controller 116 may determine the roller 104 has decoupled from the work material 102 when a magnitude of the second variance exceeds a threshold value. The threshold value may depend on operating parameters of the machine 100, such as engine speed, transmission, etc. as well as operating parameters of the work site, such as material properties of the work material 102.

In step 212, the controller 116 may take a corrective action in response to determining the roller 104 is decoupled from the work material 102. In some aspects, the controller 116 may forward an alert to an operator of the machine 100. The alert may indicate that the roller 104 has decoupled from the work material 102. The controller 116 may provide useful diagnostic information to the operator in the alert. For example, the alert may operational settings of the machine 100 at the time of the decoupling, such as an engine speed of the machine 100, a transmission setting, a vibrational frequency of the roller 104, a vibrational amplitude of the roller 104, and the like. The operator of the machine 100 may take appropriate action following receipt of the alert.

In other aspects, the corrective action may be to adjust operational settings of the machine 100. For example, the controller 116 may determine a change in the power potential of the power source 108, a setting of the vibration system 118, and the like, would allow the roller 104 to recouple to the work material 102. The controller 116 may forward instructions to an operator of the machine 100 containing operational setting changes to resume recouple the roller 104 to the work material 102. The controller 116 may determine the setting changes based on operational settings of the machine 100, such as an engine speed of the machine 100, a transmission setting, a vibrational frequency of the roller 104, a vibrational amplitude of the roller 104, and the like. For example, the controller 116 may forward instructions to reduce the vibrational amplitude of the roller 104 from a first setting to a second setting. In other aspects, the controller 116 may automatically adjust operational settings of the machine 100 without operator input.

As used herein, the controller 116 may be a processor-based device that operates by executing computer-executable instructions read from a non-transitory computer-readable medium. The non-transitory computer-readable medium may be a hard drive, flash drive, RAM, ROM, optical memory, magnetic memory, combinations thereof, or any other machine-readable medium known in the art. The controller 116 may be single device or a plurality of devices. Further, the controller 116 may be a dedicated controller or may be implemented within an existing controller also serving one or more other functions, e.g., engine or machine speed control. It will be appreciated that any of the processes or functions described herein may be effected or controlled by the controller 116.

It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.

Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. 

We claim:
 1. A compaction system comprising: a roller configured to compact a work material through rolling engagement with the work material; a propulsion device configured to propel the roller along the work material; a power source operatively coupled to the propulsion device; a sensor configured to generate a signal that is indicative of a power potential from the power source; and a controller operatively coupled to the sensor, the controller configured to: receive the signal from the sensor; determine a first variance for a first time duration of the signal; determine a second variance for a second time duration of the signal; and determine the roller is decoupled from the work material based on at least one of the first variance and the second variance.
 2. The compaction system of claim 1, wherein the controller is further configured to: compare the first variance and the second variance; and determine the roller is decoupled from the work material when a difference between the first variance and the second variance exceeds a threshold.
 3. The compaction system of claim 1, wherein the controller is further configured to determine the roller is decoupled from the work material when a magnitude of the second variance exceeds a first threshold.
 4. The compaction system of claim 1, wherein the controller is further configured to forward an alert to an operator, the alert indicating that the roller is decoupled from the work material.
 5. The compaction system of claim 1, wherein the controller is further configured to adjust the power potential of the power source when the roller is decoupled from the work material.
 6. The compaction system of claim 5, wherein the controller is further configured to adjust the power potential of the power source based on at least one of the first variance and the second variance when the roller is decoupled from the work material.
 7. The compaction system of claim 1, wherein the power source is a hydraulic power source and the signal is a hydraulic pressure signal.
 8. The compaction system of claim 7, wherein the sensor is operatively coupled to an axle drive of the propulsion device and the signal is a hydraulic pressure signal at the axle drive.
 9. The compaction system of claim 7, wherein the sensor is operatively coupled to the roller and the signal is a hydraulic pressure signal at the roller.
 10. The compaction system of claim 1, wherein the power source is an electric drive system and the signal is an electric potential signal.
 11. The compaction system of claim 10, wherein the sensor is operatively coupled to an axle drive of the propulsion device and the signal is the electric potential signal at the axle drive.
 12. The compaction system of claim 1, wherein the first variance is a first peak-to-peak variance of the signal during the first time duration and the second variance is a second peak-to-peak variance of the signal during the second time duration.
 13. The compaction system of claim 1, wherein the first variance is a first average frequency of the signal during the first time duration and the second variance is a second average frequency of the signal during the second time duration.
 14. The compaction system of claim 1, wherein the first variance is a first average frequency variance of the signal during the first time duration and the second variance is a second average frequency variance of the signal during the second time duration.
 15. A method for determining decoupling of a roller from a work material, the method comprising: compacting the work material with a roller driven by a propulsion device; receiving a signal from a sensor, the signal indicative of a power potential of a power source operatively coupled to the propulsion device; determining a first variance for a first time duration of the signal; determining a second variance for a second time duration of the signal; and determining the roller is decoupled from the work material based on at least one of the first variance and the second variance.
 16. The method of claim 15, further comprising: comparing the first variance and the second variance; and determining the roller is decoupled from the work material when a difference between the first variance and the second variance exceeds a threshold.
 17. The method of claim 15, further comprising determining the roller is decoupled from the work material when a magnitude of the second variance exceeds a first threshold.
 18. The method of claim 15, further comprising forwarding an alert to an operator, the alert indicating that the roller is decoupled from the work material.
 19. The method of claim 15, further comprising adjusting the power potential of the power source when the roller is decoupled from the work material.
 20. An article of manufacture comprising non-transitory machine-readable media having instructions encoded thereon for causing a controller to: forward instructions to compact a work material with a roller driven by a propulsion device; receive a signal from a sensor, the signal indicative of a power potential of a power source operatively coupled to the propulsion device; determine a first variance for a first time duration of the signal; determine a second variance for a second time duration of the signal; and determine a roller is decoupled from the work material based on at least one of the first variance and the second variance. 